It should be understood that in this explanation the term "battery pack" will usually refer to a collection of batteries (often 10-12 or more) usually connected in series and used to power an electric vehicle. "Battery" will be usually be used to refer to individual batteries. Colloquially, "battery" and "battery pack" are often used interchangeably in the electric vehicle field. Each "battery" is usually made up of a collection of individual "cells" within one case.
Electric vehicles have been manufactured for many years. In fact, in the very earliest days of automobiles, around the turn of this century, electric power was an equal contender with steam and internal combustion. From about the time of the First World War, however, the convenience, speed and economy of the internal combustion engine all but eliminated electric cars as a factor in the market. At the time of the gas crisis in the mid- to late- 1970's, electric cars were again in the limelight, but most of the companies then in the market faded away with the abundant gasoline and lessened government subsidies of the 80's.
Now, air pollution reduction laws have forced several states (such as California) to require that a certain percentage of cars sold be "zero pollution"--which means, in today's technology, electric.
The major drawback to electric cars which resulted in the death of the industry in the 1920's is the same one which has retarded the use of such vehicles to this day, except in very specialized applications. That drawback is the very nature of the lead-acid storage battery: weight, cost, limited lifetime, and, most of all in today's mobile society, the limited vehicle range between recharges and the time consumed by such recharging. It would be typical of modern electrics to need a charge of six or eight hours duration after less than 100 miles of relatively low-speed cruise. While adequate for a delivery truck making local deliveries with overnight charging, perhaps, such range is too short, and the recharge time too long, to attempt to use such a vehicle on even a relatively short highway trip.
Several exotic alternatives have been proposed, such as fuel cells and high-temperature sodium batteries, etc, but cost and safety factors will most likely cause the old familiar lead-acid battery in one form or another to remain the standard for some time to come.
This has led to attempts to develop improvements in battery chargers, or in the batteries, to shorten the recharge time of the battery pack to something similar to the refill time of a gas tank on today's car. Some promoters have claimed recharge times of as short as five minutes in the popular press, but a simple calculation will show that any attempt to put the energy involved in moving a vehicle 100 miles or more back into a battery pack in such a short time would involve charging currents on the order of several thousands of amperes. This would require cables and connectors of gargantuan size, and such a charge current would melt most current battery packs, not to mention the peak demand on the electric power system of a highway "gas station" charging eight or ten cars at such a rate.
One possible solution to the problem is not to recharge the battery at all--at least, not while the driver waits. Instead, one simply removes the battery pack and replaces it with a new pack, fully charged. The removed pack can then be recharged at leisure.
This elegant approach was, in fact, used commercially with the first auto taxis in New York City. There were hundreds of Columbia Electrics on the streets of New York in about 1900. When the battery pack began to run down, the cab was driven back to its garage, where the nearly a ton of battery was removed by a hydraulic lift, and a freshly-charged pack was lifted into place. (See The Treasury of the Automobile, Stein, 1961, p. 102; Wheels on the Road, Hebb, 1966, p. 71). Some of the electrics designed and marketed in the late 70's, like their remote ancestors, included provision for swapping battery packs (see Complete Book of Electric Vehicles, Shackett, 1979, pp. 84,89). In these latter-day electrics, as in the Columbias of 1900, the owner of the vehicles would have to maintain a number of sets of batteries, and appropriate lifts, to keep its fleet on the road. Because of this, the only application of swappable battery packs on electric vehicles, insofar as there has been any use of the technique at all, has been in large fleets of cabs or delivery trucks where the owner can amortize the cost of extra batteries and whatever is necessary to change them over many vehicles, or where the need to keep the vehicle constantly on the road (as in the cabs) is enough to justify the expense. For the individual electric car, to date, this has made the swappable battery pack economically prohibitive.
Once a certain minimum number of electric cars are on the road, however, whether mandated by law due to pollution laws or as a response to gasoline shortages or price, and if electric auto manufacturers agree on standardized battery packs, it would become practical for someone other than the vehicle owner to make the investment in the cost of battery packs, chargers and changing machinery. One can envision, then, a national chain of battery "gas stations" where electric car drivers can pull off the highway, drop off a depleted battery pack and install a freshly charged one, and be on their way in a matter of minutes. With such a "swappable battery" system the problems of limited range, long recharge time, and limited battery life become irrelevant.
The battery station dealer would, at a later time, charge the dropped-off battery pack at a reasonable charge rate and get it ready for the next customer. Once a pack had reached the end of its life the dealer could retire it and replace it in the stream of packs. This, then, gives rise to cost allocation issues requiring the tracking of the pack, its location and usage, which are addressed by the subject invention.
Another factor which has held back the acceptance of the electric car for the average driver is the limited life of the batteries themselves. Lead-acid batteries typically lose their ability to be fully charged and to retain their charge with age and also with the rate of charge and discharge to which they are exposed. The typical life of a practical electric vehicle traction battery should be approximately 850 recharging cycles from the fully discharged state, which would vary based upon the way the vehicle is driven. (See Chapman and Aston, "A Generic Battery Model for Electric and Hybrid Vehicle Simulation Performance Prediction", Int. Journal of Vehicle Design, Special Publication SP2, London, UK (1982), pp. 125-143; Mahato, Brilmeyer and Bullock, "Performance Testing of Advanced Lead-Acid Batteries for Electric Vehicles", Journal of Power Sources, v. 16 pp. 107-118 (1985)). This implies that the vehicle owner should not expect his traction battery, after several hundred recharges, would still give him the driving-mileage potential of a new battery. More important, from the driver's standpoint, the "fuel gauge" of the vehicle should be able to reflect this age deterioration. Further, this reduction of capacity with age currently means that the electric vehicle owner must be ready to replace the entire battery pack every 850 cycles or so--about every 3-4 years for a car used every weekday--a major expense to be considered in purchasing an electric car.
This problem of limited battery life and high replacement cost can be circumvented with the conventional (i.e. not swappable) battery packs by separating the ownership of the car and the battery, and having the car owner lease the batteries from either the car manufacturer or some third party, such as a battery manufacturer. Possibly in the future electric cars will be sold without batteries, and the purchaser will have the option of buying or leasing the pack from a number of sources. If this scenario develops, the owner of the batteries will need to keep track of the usage of the pack, for the same reasons as discussed for swappable packs.
An individual customer might be offered a number of optional methods of paying for the battery pack based on his own usage patterns, whether in a conventional system with leased batteries, or in a swappable pack system. The customer could pay a flat annual "rental" fee on the packs, or he could be billed periodically based on the amount of the battery pack's "life" he had "used up" in his driving. This latter method would take into account the factor that battery life is affected by how it is used--a driver who draws heavy current from the battery by high speeds or rapid acceleration and drains the pack nearly dry before recharging would pay more than a driver who uses only small currents in short, low speed city trips. In addition, a "usage" fee could be assessed based on the amount of energy consumed, or the amount of energy used by the dealer in charging the battery.
Accumulation of usage history for the battery pack would also allow a more accurate "on the fly" estimation of remaining range--an important factor for the driver.
In addition, most car owners and drivers do not keep very good statistics about the use of their vehicles. The accumulation of usage history information is of importance to the car owner/driver for the purpose of tracking maintenance intervals and time to replace the pack, and to monitor and perhaps give warning of pack deterioration.
The customer might recharge the battery pack at home overnight, as well. If such recharging is done, and it would seem that in many applications it would be desirable, the battery supplier would need to take this into account when billing and accounting for the health and usage history (rate and number of charge/discharge cycles) of the pack.
If the swappable system were to be adopted, the battery pack dealer would most often see the pack at recharging time, perhaps after it has been removed from the vehicle. In such a case it would be necessary for the dealer to be able to identify the last user of the pack once it has been removed.
It is also possible that, if the electric car should become a significant portion of the cars on the road, that either municipal or private parking lots might find it advantageous to provide charging facilities at some or all of the parking spots in a lot by providing charging posts very similar to parking meters. If they were to do so, there would need to be some mechanism for having the driver pay for the energy consumed. While a simple coin-operated mechanism might work, or a credit card reader, it would be better if the car owner were simply billed for the energy as part of his periodic battery bill with no more effort than simply plugging the battery pack into a charging socket.
It is thus the object of this invention to provide a device for implementing a method of gathering information on battery charge and usage, which is associated with the battery pack, and is independent of the car electronics. Such information can then be used in a system of billing for pack usage and/or energy consumption, as well as optionally providing for an accurate running estimate of remaining charge and/or battery life for the driver of the vehicle.
The prior art, as explained above, does not, to the inventor's knowledge, describe any such device in any traction battery system, whether for a swappable "battery swap" system, or for the more conventional fixed pack approach. The reason for this is simple--in all of the cases of replaceable traction batteries for electric vehicles known to the inventor, there was no need to track individual packs or vehicles, or to bill usage, since all of the vehicles and packs were owned by a single fleet. In conventional systems, the battery pack has always been owned by the vehicle owner, again, primarily in fleets. Although there might be some usefulness in the invention to a fleet operation (especially in third-party battery leases), the invention is primarily directed to a market which has not hitherto existed--the rental of battery packs to individual vehicles, where the ownership of the batteries is in an entity other than the car owner. The invention also has applicability to battery pack usage outside of the vehicle field, such as remote transmitters, backup power, etc.
Some method will need to be set up to allow national or regional usage of electric vehicles. If the battery swap system does not evolve, some sort of central billing for recharging services will have to be developed. An electric car owner will want to be able to plug into a standardized charging station anywhere in a wide geographic area, and be able to receive a bill later, in the same way as he receives gasoline credit card bills today. The owner of the battery pack will want some method of accumulating the statistics about the usage of the pack, so that he can notify the car owner when the pack has aged to the point where it is necessary to change the pack.
If the swap system is developed, it will need to become broadbased. Few electric vehicle users will want to be limited to a single local battery replacement center. It may happen that more than one company may arise to supply the roadside replacement or recharge service, and a user will swap packs only at stations belonging to the company with which he has a contract. Alternatively, a national franchise concern might be implemented, with local ownership of replacement centers, who will share battery packs belonging to the franchiser among the franchise (perhaps like today's one-way rental trucks). Or the batteries may circulate freely among many unrelated vendors, with accounting handled through a central clearing house, somewhat analogous to the system used for railway boxcars. By keeping information about the identity of the pack, and the history of the users, the invention will facilitate the implementation of whatever system should evolve.